LOS ANGELES, California (CNN) -- The Los Angeles Coroner's chief investigator revisited the office of Michael Jackson's dermatologist Wednesday, even though the coroner announced last week his "thorough and comprehensive" report was completed.

Dr. Arnold Klein denied in a CNN interview last month that he had given Jackson dangerous drugs.

Winter, who also visited Klein's office on July 14, said the doctor's staff and lawyers cooperated with his requests.

Garo Ghazarian, one of Klein's two lawyers on the scene, said the doctor did not meet with Winter.

"They had inquiries born out of information they wanted to corroborate," Ghazarian said.

Ghazarian said he was added to Klein's legal team "to take a look and see if there's any cause for concern in light of media reports" that investigators were considering criminal charges against him.

"I have seen no cause for concern on behalf of my client, Dr. Arnold Klein," Ghazarian said.

The coroner's office said more than a week ago that a "thorough and comprehensive" report into the death of Michael Jackson is complete, but police have requested that the report not be released yet because of the ongoing criminal investigation.

The coroner's office said it would abide by the request that "the cause and manner of death remain confidential," and referred all questions to the Los Angeles Police Department.

Murray, a cardiologist, owned and operated two medical clinics -- in Las Vegas, Nevada, and Houston -- but he took a full-time job as Jackson's personal doctor in May, as the pop singer prepared for his comeback concerts scheduled to start in July.

Investigators have searched Murray's home and clinics for evidence related to the anesthetic propofol, according to documents filed in court. A source close to the investigation told CNN it's believed Murray administered the drug, also known by the brand name Diprivan, to Jackson within 24 hours of his death.

Ed Chernoff, Murray's lawyer, said it was only after Murray moved to Los Angeles in May 2009 that "he realized that Michael Jackson had some very unusual problems."

Chernoff, in comments published in the Los Angeles Times and confirmed by his spokeswoman, said that when Murray took the job, his client did not know what drugs Jackson might have been taking or whether he was addicted.

Murray did not conduct drug tests on Jackson and had no way of knowing, other than from Jackson's words, if he was taking other drugs, Chernoff's spokeswoman, Miranda Sevcik, told CNN.

One of the warrants used in searches of Murray's home and clinics implied that police suspect Jackson was a drug addict.

Chernoff has refused to confirm or deny whether Murray administered propofol to Jackson, although he denied "unequivocally" that Murray gave Jackson painkillers.

A former prosecutor who has also defended doctors in medical malpractice cases involving anesthesia said prosecutors would face "a very, very severe uphill battle" when charging a doctor with manslaughter.

"You have to prove gross recklessness in the prescription of drugs," Paul Callan told CNN. "That's really hard with a doctor because doctors are always prescribing drugs; patients occasionally die from them. That's not criminal conduct. But here, you have to show that this doctor should've known Jackson was an addict and that he could've died from these drugs."